Because of the severe stress put on the ignition of rocket engines in rocket powered systems, gas turbine engines, and other similar combustion devices, and the catastrophic result of a failure to timely and reliably ignite them, there has always been a need for a reliable engine igniter which would be able to be accurately timed to ignite when desired.
Piezoelectric crystals have been used commonly as spark ignition sources for stoves and barbeque lighters, but the actuation mechanism usually consists of a mechanically actuated hammer that is driven by some sort of spring mechanism.
Prior piezoelectric ignition systems have been patented but in prior patented devices it is not clear that as a practical matter sufficient force will be generated by any of the described methods, or that the impulse applied to the crystal will be of sufficient magnitude or be applied at a rapid enough rate to produce a strong spark.
Information relevant to attempts to address these and other problems can be found in U.S. Patent Application and U.S. Pat. Nos. 2009/0236441 A1, 2009/0173321 A1, 7,578,279 B2, 7,565,795 B1, 7,555,938 B2, 7,397,170 B2. However, each one of these references suffers from one or more of the above disadvantages related to insufficiency of spark strength:
In an attempt to produce a satisfactory spark strength, some prior patents have attempted to solve this problem by describing possible methods of spreading the gas pressure over a larger area, and attempting to increase the force applied to the piezoelectric crystal proposing to use impingement of the gas force directly onto the piezoelectric crystal, or through an attached intermediary connecting element, but to date none of these prior inventions have been practically successful in solving this problem. Others have used a fluidic oscillator as a means of repetitively exciting a piezoelectric crystal, however a description of such a necessary fluidic oscillator is not provided. Specifically, although force conveying elements means connecting the source of fluid pressure to the piezoelectric crystal are mentioned, no actual specific means of using the fluid pressure to accelerate a solid mass to a high enough velocity, so as to subsequently impact the crystal or connected force conveying elements, is specified. A specific method, hitherto unknown, is critical for actually being able to obtain a sufficiently strong, reliable spark from the piezoelectric crystal of sufficient strength to ignite a rocket engine, a gas turbine engine, or other combustion device and this is precisely what the embodiment of the present invention disclosed in this patent provides.
The embodiment of the present invention presently disclosed overcomes these shortcomings by retaining a hammer ball in a controlled manner until sufficient energy has been stored in the actuating gas to then accelerate the hammer ball to sufficient velocity to attain sufficient rapid impulse necessary to obtain a strong piezoelectric crystal response.
Although the shape of the hammer element in the preferred embodiment is referred to as a ball, and it is presently envisioned that this spherical shape might be desirable, it is by no means the only shape that might be employed for the sliding hammer element.
For the foregoing reasons, there is a need for a specific method to produce a sufficiently and reliably strong spark response so as to be able to ignite a rocket or other similar type of propulsion system.